Fault-locator for electric cables.



No. 754,402. PATENTED MAR. 8, 190 D. E. WISEMAN. FAULT LOGATOR FORELECTRIC GABLES.

APPLICATION FILED AUG. 3, 1903.

N0 MODEL. 2 SHEETS-SHEET ll mvweyx No. 754,402. PATENTED MAR. 8, 1904.

D. E. WISEMAN.

FAULT LOGATOB. FOR ELECTRIC GABLES.

APPLICATION FILED AUG, s, 1903.

N0 MODEL. 2 SHEETS-SHEET 2 EJ I v i I III I E UNITED STATES PatentedMarch 8, 1904.

PATENT OFFICE.

FAULT-LOGATOR FOR ELECTRIC CABLES- srnolmoarxon forming part of LettersPatent No. 754,402, dated March a, 1904.

Application filed August 3, 1903.

To all whom it may concern.-

Be it known that I, DANIEL E. WISEMAN, a citizen of the United States,residing at Spokane, in the county of Spokane and State of Vashington,have invented a certain new and useful Improvement in Fault-Locators forElectric Gables, of which the following is a full, clear, concise, andexact description.

My invention relates to cable-testing appa ratus; and its object is toprovide improved means for quickly locating faults, such as crosses,grounds, or breaks in the cable-con ductors. Y

More particularly my object is to avoid the necessity of calculation onthe part of the operator, and I have invented an apparatus by means ofwhich the distance from the end of the cable to the fault may be readdirectly upon a scale in units of distance.

Generally'speaking, my invention contemplates the use of a resistancearranged to be divided into two branches or ratio-arms of a\Vheatstone-bridge circuit by a movable con tact, the faulty conductorbeing connected with said resistance, so that the portions of saidconductor on either side of the fault are included, respectively, in theother two arms of said heatstone-bridge circuit. The testing instrumentis included in the bridge in the usual way, and a suitably-connectedsource of testing-current is provided. In this arrangement when abalance is obtained such that no current flows through the bridge containing the testing instrument it will be apparent that the proportionsof the resistance in the respective ratio-arms will correspond with theportions of cable-conductor on either side of the fault, so that thelocation of the fault can be determined with considerable accuracy. Inaccordance with my invention I divide the total resistance of the tworatio arms of the Wlieatstone bridge into a number of arbitrary unitscorresponding to the number of units of distanceit may be feet, oryards, or milesin, the length of cable being tested. When the movablecontact-terminal which divides the total operative resistance into tworatio-arms is moved to such a point on the resistance thata balance isobtained in the bridge containing the testing instrument,

Serial No. 167,963. (No model.)

it will be apparent that the number of units of resistance in therespective ratio-arms will then indicate directly the number of units ofdistance from the ends of the cable to the fault. I preferably provide aresistance divided into a number of equal partssay one thousandwith acorrespondingly divided scale and acontact-terminal which isv adapted tobe set at any point along said resistance until the number of units ofresistance brought into circuit, as shown by the scale, corresponds tothe number of units of length in the condu'ctor being tested. The othermovable contact, which determines the relative distribution of thisoperative resistance in the two ratio-arms, may then be adjusted until abalance is obtained, and the position of this second-mentioned contacton the scale will then indicate in units of length the distance from theend of the cable to the fault.

I will describe my invention by reference to the accompanying drawings,in which Figure 1 is a diagram illustrating the apparatus adapted foruse in testing for either breaks or crosses in the cable-conductors.Fig. 2 is a simplified diagram illustrating the use of the apparatus inlocating a cross. Fig. 3 is av similar simplified diagram showing theuse of the apparatus in locating a break. Fig. 4 is a view in elevationof a rheostat having two movable contact-arms moving over theuniformlydivided resistance and the scale indicating the divisions ofsaid resistance, and Fig. 5 is a detail sectional view showing theconstruction of the rheostat.

The same characters of reference are used to designate the same partswherever they are shown.

By reference to Figs. 2 and 3 the circuits for making the test will beeasily understood. The resistance 1*, which is divided uniformly into anumber of arbitrary units, is connected with the ends of the faultyconductor a Z; and with the terminals of a source of current in such away that the resistance and said con ductor a b are in parallel branchesof the circuit. The testing instrument, which may be a galvanometer g intesting for crosses or a telephone t in testing for breaks, is connectedin a bridge-conductor 6, one terminal of which is connected to thesheath of the cable or'the bunch of other wires, while the otherterminal is connected. to a movable contact d, which is adapted to beadjusted to any point along the uniformly-dividedresistance 'r. Theoperative length of the resistance 7', which is in-' cluded in the tworatio-arms of. the Wheatstone-bridge circuit, is determined by theposition of a movable contact e, which forms the terminal'of a conductor7, leading from the end a of the conductor a b. The other end 6 of saidconductor is connected to the end f of the resistance.

In Fig. 2 a cross of the conductor a b with the sheath 0 of the cable isindicated at m, and in Fig. 3 :1: indicates a break in the conductor ab. 1 In the arrangementof Fig. 2 when the contact (1 is at such aposition along the resistance 1- that-a balance is obtained and nocurrent flows through the bridge 6 it is evi of resistance in theportion d f will be the same'as the number of units of length in theportion of conductor a b from the end bto the cross w; "Thelocation ofthe fault may therefore :be readdirectly from the location of themovable contact d upon the scale, which indicates the number ofarbitrary units of resistance included in the ratio-arm d f. Fig.

. .3 shows 'asimilar arrangement for determining the location of a breakin conductor a b. In thiscase the current is derived from the secondarys -of an,induction-coil, the pri-' first set at such a point that thenumber of ar- -bitrary units in the operative portion a f of theresistance r will correspond with the number of units of length in theconductor a b.

The movable contact all is then shifted along the resistance runtil itreaches a point where no sound is heard in the telephone 25. The

ratio of the resistance (Z f to the resistance 6 d corresponds to theratio of capacity a w to capacitybw.

In Figs. 4 and 5 I have shown a rheostathaving two movable contact-armsd e, which are pivoted to move overa scale divided into one thousandparts. These arms are insulated from each other at their common pivot,as shown, and the contact-shoes upon their outer ends bear upon thecontact-terminals 1- r of a resistance 7', which may be wound uponsuitable pegs at the back of the rheostat-frame.

sources of testing-current.

corresponding to the one thousand points on the scale. The circuits andapparatus used with this rheostat are 'shown in Fig. 1. The testinginstrument to be used may be either a galvanometer g or a telephone t,and I have illustated a telephone switch-hook adapted to bring theseinstruments alternatively into circuit. When the telephone is on itshook, the galvanometer g is included in the bridge, and when thetelephone is taken from its hook said galvanometer is disconnected andthe telephone-receiver substituted therefor. binding-posts h it Z areprovided for connecting the testing instruments with the cable. Thebinding-posts h and Z are to be connected with the ends of the faultyconductor of the cable, while the post k should be connected to thesheath and to the bunch of other conductors. The binding-post l isconnected with one end f of the resistance 1, the extreme end of saidresistance being open, and the binding-post k is connected with themovable contact-arm e, which thus determines the operative portion ofresistance 1", which is connected with the terminals of thefaulty'conductor.

Three The other movable contact-arm dof the rheostat forms the terminalof a bridge-circuit 6, extending to the binding-posts k and divided intotwo parallel branches 7 8, which are adapted to'be alternatively closedby the telephone-switch m, the branch 7 containing the galvanometer,being normally clpsed when the telephone is on its hook. When thetelephonereceiver is taken from its hook, the branch 7 is opened atcontact m and the branch 8 closed at contact m The telephone-switch on.also controls the application of two diflerent When the telephone is onits hook, the test-battery Z is connected in a circuit Q-between thebinding-posts h and Z, the continuity of this circuit beingcontrolled'by the contact m; but when the telephone is taken from itshook the contact m is broken and another circuit 10 between said bindingposts h l established at the contact 971., said circuit including thesecondary s? of an induction-coil s. The primary 8 of saidinduction-coil is in a local circuit 11 with a battery Z and interrupteri, said local circuit being also'closed at a contact m when the.

telephone is taken from the hook.

The operation of testing acable with this apparatus is extremely simple.Assuming the fault to be a cross or ground, the inside end of the cableis connected to the bindingpost It and the outside end to thebinding-post izo ber of units of length in the cablethat is to say,assuming the cable to be eight hundredand fifty feet long, the arm 6would be set at the figures 850. The fault in this case being across orground the test will be made with the galvanometer, so that thetelephone being on its hook the arm d will simply be moved along thescale until the galvanometer shows no deflection. A balance being thusobtained the distance of the cross from the outside end of the cable isthen indicated by the figures on the scale where the contact-arm drests. In Fig. 5 the contact-arm e is shown resting on the point 850 ofthe scale, while the contact-arm d rests on. the point 250. If a balancewere obtained under these conditions, it would'therefore mean that thecross was located two hundred and fifty feet from the outside end of thecable. In testing for breaks the connection of the cable withbinding-posts hand Zis reversedthat is, the outside end is connected tobinding-post h and the inside end to binding-post Z. The contact-arm ebeing adjusted, as before, to indicate on the scale the length of thecable, the telephone t is taken from the hook, and the operator whilelistening in the telephone moves the contact-arm d until the minimumsound of the alternating current from the induction-coil winding 8 isheard. The figures on the scale where the contact-arm d rests willindicate, as before, the distance in feet from the outsideend of thecable to the break.

The advantages of this testing apparatus will be easily apparent. Nomathematical calculations are necessary to determine the location of thebreak. It is read directly on the scale. Only one reading is necessary,and this may be taken by an ordinary unskilled person. In order-tolocate a fault with accuracy by any-method, the several parts should betested under exactly the same electrical conditions, and with myapparatus such a test is made, because the defective parts are balancedagainst each other at the same moment.- Trouble'caused by jarring thegalvanometer in locating breaks by the old methodis done away with, andbecause of the accuracy and rapidity of operation of my instrument muchtime is saved in repairing faulty cables.

Having thus described my invention, I claim 1. In a fault-locator forelectric cables, the combination with a resistance and a movable contactadapted to divide the same into two branches, of means for connectingsaid branches to form two ratio-arms of a Wheatstone-b'ridge circuit,the faulty conductor of the cable being connected so that the portionson either side of the fault are included respectively in the other twoarms of said Wheatstone bridge, a testing instrument in the bridge, asource of current, and means for dividing the total operative resistanceinto a number of units corresponding to the number of units of length ofthe faulty conductor, whereby when a balance is indicated by saidtesting instrument, the number of units of resistance in the ratio-armsindicate directly the distance in units of length from the ends of thecable to the fault.

2. In a fault-locator for electric cables, the combination with aresistance and a corresponding scale divided to indicate the units ofresistance, of a movable contact e adapted to be adjusted along saidresistance, said movable contact and the other end of the resistancebeing adapted to be connected respectively with the terminals of thefaulty conductor of the cable, said contact 6 being adapted to beadjusted along the scale to bring into the circuit a number of units ofresistence corresponding to the units of length of the cable, a secondmovable contact d adapted to be adjusted along the operative resistancedetermined by said contact 6, a source of current, a testing instrument,and connections forming a Wheatstone-bridge circuit in which theportions of the resistance on either side of the said contact (Z formtwo ratio-arms and the portions of the cable-conductor on either side ofthe fault form the other two arms, the testing instrument being locatedin the bridge, whereby the position of said contact 6! when a balance isobtained indicates the location of the fault directly upon the scale.

3. In a faultlocator for electric cables, the combination with aresistance 1', of a movable contact 6 adapted to be adjusted along saidresistance, said movable contact and the other end of the resistancebeing adapted to be connected respectively with the terminals of thefaulty conductor of the cable, said contact e being adapted to beadjusted along the scale to bring into the circuit a number of units ofresistance corresponding to the units of length of the cable, a secondmovable contact d adapted to be adjusted along the operative resistancedetermined by said contact 0, connections forming a Wheatstone-bridgecircuit of which the portions of resistance 1' on either side of contactd form two ratio-arms, the portions of the cable-conductor on eitherside of the fault forming the other arms, a testingbridge 6 having twobranches, one of said branches containing a galvanometer and the otherbranch containing a telephone instru ment, a telephone-switch adapted toclose said branches alternatively, a source of direct current Z andasource of varying current .9 arranged to be connected alternatively inthe circuit according to the position of said telephone-switch. I

In witness whereof I hereunto subscribe my name this 2d day of July, A.D. 1903.

. DANIEL E. WISEMAN.

